This project represents an attempt to gather longitudinal data regarding overnight sleep and daytime sleepiness in two groups of children/adolescents. The first group includes children with no sleep complaints and no family history of sleep disorders. The second group includes children who are at risk for the development of pathological sleepiness by virtue of having one parent who has narcolepsy. We have found in the control group that midpubescence is a time of life at which subjects are sleepy during the day in spite of sleeping as much at night as prepubertal subjects. In addition, we have documented the development of narcolepsy in one child whose mother has the disorder. Preliminary results of the project suggest: (1) that we may be able to assess the likelihood of developing narcolepsy in children at risk for the disorder; and (2) that naps may be useful as a nondrug therapy for excessive daytime somnolence in adolescents.